Engineering the PEM Water Electrolysis Anode for Better Interfacial Electrical Conductivity

In pursuing cost-effective green hydrogen production via proton exchange membrane water electrolysis (PEMWE), the high expense of the iridium (Ir)-based oxygen evolution reaction (OER) catalysts poses a significant challenge. To overcome this issue, researchers have focused on developing active OER catalysts and catalyst layers (CLs) with minimum uses of Ir. However, they frequently encountered performance problems at the single-cell level that originate not only from the kinetic polarization but also from the ohmic polarization. In this aspect, we have focused on identifying the reasons for the poor performance of low IrO x -loaded anodes, with loadings as low as 0.10 mg cm -2 . We pinpoint the cause of the poor performance of the low loaded anodes to an electron transport problem within the native oxide on the Ti porous transport layer (PTL). Our analysis, grounded in the metal-insulator band model, reveals that the primary factors contributing to electron conductivity loss in the Ti oxide are the upward band bending induced by the Schottky contact with high work function IrO x and by the pinch-off effect from the extensive ionomer contact. Based on the above understanding, we propose an anode CL composed of a one-dimensional iridium catalyst, fabricated by electrospinning and calcination processes. Our nanofiber-based CL effectively mitigates the electron transport problem of the native Ti oxide. This improvement stems from the low work function of the Ir nanofiber catalyst and the highly porous structure that reduces the ionomer contact with the Ti oxide. Furthermore, the highly porous nature of the nanofiber-based CL enhances two-phase mass transport, facilitating the high current operation. These findings underscore the critical role of the CL/PTL interface of the PEMWE anode and present the necessity of a well-structured CL to achieve efficient and cost-effective water electrolysis.